<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>

  <div id="root"></div>
  
  <!-- 引入依赖 -->
  <script crossorigin src="https://unpkg.com/react@18/umd/react.development.js"></script>
  <script crossorigin src="https://unpkg.com/react-dom@18/umd/react-dom.development.js"></script> 
  <script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>

  <!-- 编写React代码 -->
  <script type="text/babel">
    const root = ReactDOM.createRoot(document.querySelector("#root"))

    // 1.将文本定义成变量
    let message = "Hello World"

    // 2.监听按钮的点击
    function btnClick() {
      // 1.1.修改数据
      message = "Hello React"

      // 2.重新渲染界面
      rootRender()
    }

    // 3.封装一个渲染函数
    function rootRender() {
      root.render((
        <div>
          <h2>{message}</h2>
          <button onClick={btnClick}>修改文本</button>
        </div>
      ))
    }
    rootRender()

  </script>

</body>
</html>